numbck.f

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C> @file
C> @brief Check the validity of an FXY value
C>
C> @author Woollen @date 1994-01-06
 
C> This function checks the input character string to determine
C> whether it contains a valid FXY (descriptor) value.
C>
C> @param[in] NUMB - character*6: FXY value to be checked.
C>
C> @return indicator as to whether numb is valid:.
C> - 0 yes
C> - -1 no, the first character ("F" value) is not '0', '1', '2', or '3'
C> - -2 no, characters 2-6 ("X" and "Y" values) are not all numeric
C> - -3 no, characters 2-3 ("X" value) are not between '00' and '63'
C> - -4 no, characters 4-6 ("Y" value) are not between '000' and '255'
C>
C> @author Woollen @date 1994-01-06
      FUNCTION numbck(NUMB)
 
      CHARACTER*6  numb
      LOGICAL      digit
 
C-----------------------------------------------------------------------
C-----------------------------------------------------------------------
 
C  CHECK THE FIRST CHARACTER OF NUMB
C  ---------------------------------
 
      IF( llt(numb(1:1),'0') .OR. lgt(numb(1:1),'3') ) THEN
         numbck = -1
         RETURN
      ENDIF
 
C  CHECK FOR A VALID DESCRIPTOR
C  ----------------------------
 
      IF(digit(numb(2:6))) THEN
         READ(numb,'(1X,I2,I3)') ix,iy
      ELSE
         numbck = -2
         RETURN
      ENDIF
 
      IF(ix.LT.0 .OR. ix.GT. 63) THEN
         numbck = -3
         RETURN
      ELSE IF(iy.LT.0 .OR. iy.GT.255) THEN
         numbck = -4
         RETURN
      ENDIF
 
      numbck = 0
 
      RETURN
      END